Fix inconsistent use of PinnedRemotableDataScope and the snapshot stream

src/EditorFeatures/TestUtilities/Remote/InProcRemostHostClient.cs

@@ -63,7 +63,7 @@ protected override async Task<Session> TryCreateServiceSessionAsync(string servi
         {
             // get stream from service hub to communicate snapshot/asset related information
             // this is the back channel the system uses to move data between VS and remote host
-            var snapshotStream = await _inprocServices.RequestServiceAsync(WellKnownServiceHubServices.SnapshotService, cancellationToken).ConfigureAwait(false);
+            var snapshotStream = getSnapshotAsync.Value == null ? null : await _inprocServices.RequestServiceAsync(WellKnownServiceHubServices.SnapshotService, cancellationToken).ConfigureAwait(false);
 
             // get stream from service hub to communicate service specific information
             // this is what consumer actually use to communicate information

src/VisualStudio/Core/Next/Remote/JsonRpcClient.cs

@@ -7,6 +7,7 @@
 using System.Threading.Tasks;
 using StreamJsonRpc;
 using Microsoft.CodeAnalysis.Remote;
+using Roslyn.Utilities;
 
 namespace Microsoft.VisualStudio.LanguageServices.Remote
 {
@@ -22,6 +23,8 @@ internal class JsonRpcClient : IDisposable
         public JsonRpcClient(
             Stream stream, object callbackTarget, bool useThisAsCallback, CancellationToken cancellationToken)
         {
+            Contract.Requires(stream != null);
+
             var target = useThisAsCallback ? this : callbackTarget;
             _cancellationToken = cancellationToken;
 

src/VisualStudio/Core/Next/Remote/JsonRpcSession.cs

@@ -72,6 +72,8 @@ internal class JsonRpcSession : RemoteHostClient.Session
             CancellationToken cancellationToken) :
             base(snapshot, cancellationToken)
         {
+            Contract.Requires((snapshot == null) == (snapshotStreamOpt == null));
+
             // get session id
             _currentSessionId = Interlocked.Increment(ref s_sessionId);
 

src/VisualStudio/Core/Next/Remote/ServiceHubRemoteHostClient.cs

@@ -119,7 +119,7 @@ protected override async Task<Session> TryCreateServiceSessionAsync(string servi
         {
             // get stream from service hub to communicate snapshot/asset related information
             // this is the back channel the system uses to move data between VS and remote host for solution related information
-            var snapshotStream = getSnapshotAsync.Value != null ? null : await RequestServiceAsync(_hubClient, WellKnownServiceHubServices.SnapshotService, _hostGroup, _timeout, cancellationToken).ConfigureAwait(false);
+            var snapshotStream = getSnapshotAsync.Value == null ? null : await RequestServiceAsync(_hubClient, WellKnownServiceHubServices.SnapshotService, _hostGroup, _timeout, cancellationToken).ConfigureAwait(false);
 
             // get stream from service hub to communicate service specific information
             // this is what consumer actually use to communicate information